The truth is that healthcare reform is a very confusing and highly technical topic. Americans may support a policy presented in one form, but not in another. Americans may approve of certain individual policies of Obamacare right now, but may not once a strenuous debate takes place. For many, Obamacare remains for the most part an abstraction, which they find hard to judge without having directly felt the effect of several key measures, such as the individual mandate.I think that's true on all sides -- it applies to the unpopular mandate, and it applies to popular provisions, too -- sure, everyone loves the idea of getting rid of pre-existing conditions, but do they like the particular way ACA does it, including the trade-offs involved? For almost everyone, it's just guessing, or responding to code words. We can get a fair idea of what people don't or didn't like about the health insurance market, but what you want to know about whether ACA would ultimately be popular -- if the Court lets it try -- will come more from policy analysts at this point, not voters at large.
Particularly useless, it seems to me, are polls such as the NBC/WSJ one out now asking people for their anticipated reactions to Thursday's SCOTUS ruling. I hate this kind of poll: people don't always predict their reactions very well! Of course, all they're really tapping into is another way of asking whether people like ACA or not, and that overall question we know pretty well by now, Of course, since there's every possibility that the actual decision will be more complicated than simply affirm or reject the law (or even affirm or reject the mandate), there's not much point in anyone figuring out how they'll react.
Regardless: in terms of electoral effects, what will matter, if anything, won't be anyone's initial reaction to a Supreme Court decision. Best bet? Ignore those polls!